It is desirable to achieve high speed data transfer over circuit-switched channels at a rate above the rate available on any one circuit-switched channel. Although the capability currently exists, solutions have been costly.
An existing hardware solution is illustrated in FIG. 1. This method requires one or more external terminal adapters, a multiplexer, cabling, and a sync board for a PC. The system's cost is directly proportional to the available bandwidth.
Additionally, U.S. Pat. No. 4,387,271, issued to Artom, discloses a combined telephone and data-transfer system. The system makes use of common data network and data retrieval units to effect transmission of data on subscriber lines at frequencies outside the voice band. The data is divided into groups which are preceded by an address code.
U.S. Pat. No. 4,688,168, issued to Gudaitis et al., discloses a high speed data transfer method and apparatus. The apparatus includes a bus master controller which sequences through source and destination addresses at a rate greater than the connected units' ability to transfer data, thereby enhancing the speed of data transmission. The high speed data bus includes separate data transfer and master control bus portions.
U.S. Pat. No. 4,827,409, issued to Dickson, discloses a high speed interconnect unit for a digital data processing system. The interconnect unit includes a bus for transferring both control and user information between the unit and an external device. A simplified protocol accommodates "stalls" between the communicating devices during transfer.
U.S. Pat. No. 4,866,703, issued to Black et al., discloses an ISDN module having a time division multiplexed (TDM) switching network. Facility interface cards connect subscribers to the TDM network and provide for two-wire and four-wire subscriber connections, T1 line connections and three port conferencing arrangements. Subsystems are connected by an Ethernet LAN, allowing the system to provide both Primary Rate and Basic Rate Interfaces to subscribers.
U.S. Statutory Invention H586, issued to Kun, discloses an ISDN D-Channel handler. The ISDN network utilizes TDM and the handler, in an exchange termination (ET) collects and distributes D-channel data to various subscriber lines. A translator accesses the data and passes supervisory and signalling information contained therein to a central processor in the ET. This information is then formatted according to the International Telegraph and Telephone Consultative Communication (CCITT) standard and transmitted to the intended subscriber on the appropriate D-channel.
U.S. Pat. No. 4,878,216, issued to Yunoki, discloses a method for the management of logical channels for ISDN packet service between and ISDN and subscribers. The method allocates a logical channel group number (LCGN) in the ISDN in advance for each piece of data terminal equipment in a subscriber station. The terminal equipments notifies the ISDN of the LCGN, enabling the ISDN to offer communication service without separate management of the each piece of data terminal equipment at each subscriber site.
U.S. Pat. No. 4,914,574, issued to Terada et al., discloses a data transmission apparatus having cascaded data processing modules for daisy chain data transferring. The apparatus utilizes a plurality of data processing modules, each functional as a computer. Required sequence setting of the input/output ports of each module is performed by a port sequencer. The daisy chain transfer of the selective, load distribution and collective data transfers is combined between the data processing modules, thereby resulting in a high speed and efficient data transmission.
U.S. Pat. No. 4,937,734, issued to Bechtolsheim, discloses a high speed bus with a virtual memory data transfer and rerun cycle capability. A virtual memory scheme allows high speed data transfer, minimizing the number of lines required to implement the bus. The idle time of a particular device is also minimized.
U.S. Pat. No. 4,970,723, issued to Lin, discloses an ISDN basic rate interface (BRI) arranged for quad voice operation. The ISDN BR is interposed between a switch and a plurality of voice or data terminals, thereby enabling at least three voice terminals (or a data terminal and two voice terminals) to operate simultaneously through the B-channels of the BRI to the switch. To allow for the service, voice samples are digitized by a code converter.
U.S. Pat. No. 4,985,891, issued to Fujiwara et al., discloses an ISDN system having a subscriber line multiplexer with means for reducing the load on an ISDN switch by establishing different data links through D-channels on the subscriber line. The multiplexer comprises subscriber interfaces connected to digital subscriber lines (DSLs) and statistically multiplexes a plurality of signals for Link Access Procedure on D-channels (LAPDs) to form an additional data link between each subscriber interface and the ISDN switch, thereby reducing the load on the ISDN switch.